1. Field of the Invention
The present invention relates to a technique for updating entries of database, and particularly relates to the database system, a method and a program for creating a time-based reverse look-up table which effectively accelerates retrievals of entries of the database.
2. Background Art
Optimizing database searches has been the subject of much research. Indeed, every major database maker has devoted much time and energy to such optimizations. Searching individual databases has become a specific of implementation, since optimizations are so highly keyed to specific database structures.
The database and data stored in the database become more and more huge and the database systems are more and more utilized by a distributed computing environment. In such a circumstance, users of the database system have to pay attention to the time dependent correlation of the databases and then it is requested to enhance the search efficiency of database in which entries are updated or evolved with respect to time elapse.
Japanese Patent Laid-Open No. 2001-312505A by, Kobayashi et. al. and assigned to the same assignee of the present invention discloses the search/retrieval system of items in the database in which the items are evolved with respect to time. In the disclosed system, the items are stored as a binary data including timestamps and then a time window is added in the search query to retrieve the time weighted items. However, the disclosed method does not use any indexing data structure prepared separately with the items searched. Japanese Patent Laid-Open No. 2001-312505A